Median filtering is used to remove unwanted data from a signal. In an automotive application, a median filter can be used to remove low frequency extraneous engine and driveline vibrations from an acceleration signal used to predict combustion misfiring. An example of a system using median filtering in a misfire detection system is disclosed in U.S. Pat. No. 5,515,720 to Remboski et al. The median of a moving window of acceleration data is subtracted from the acceleration data to provide a nonlinear, high-pass filtering of the acceleration data.
Although prior art median filters are effective in removing unwanted signals, prior art approaches are very resource intensive. This makes these schemes not only silicon-complex and expensive, but difficult to manufacture and less reliable than desired.
What is needed is a simpler approach to median filtering that is less silicon-complex, easier manufacture and more reliable.